Method and apparatus for cleaning containers

ABSTRACT

A machine for cleaning containers such as flat media carriers has inside and outside arrays of nozzles arranged to spray a cleaning solution onto containers supported on a spinning rotor in a chamber. The cleaning solution, a mixture of water and a detergent or surfactant, is prepared by drawing out surfactant from a surfactant bulk storage vessel with a metering pump. The flow rate of the water is measured by a flow meter and in combination with the metering pump, a proper amount of surfactant is injected into the water line to produce a mixture with a desired surfactant concentration for removing contaminants. The mixture is injected into the water line at a mixing control valve to ensure that the water and surfactant are thoroughly mixed before being injected into the media carrier.

This Application is a Divisional of U.S. patent application Ser. No.10/043,716, filed Jan. 9, 2002, and now pending, which is a Continuationof U.S. patent application Ser. No. 09/905,030, filed Jul. 12, 2001, andnow abandoned, which is a Continuation-in-Part of:

U.S. patent application Ser. No. 09/113,440, filed Jul. 10, 1998, nowU.S. Pat. No. 6,432,214; and U.S. patent application Ser. No.09/658,395, filed Sep. 8, 2000, now U.S. Pat. No. 6,797,076.

FIELD OF THE INVENTION

The field of the present invention relates to cleaning apparatus forrinsing and drying containers and carriers used to hold and processsemiconductor wafers, substrates, flat panel displays and other flatmedia.

BACKGROUND OF THE INVENTION

Flat media, such as silicon or other semiconductor wafers, substrates,photomasks, flat panel displays, data disks, and similar articlesrequire extremely low contamination levels. Even minute contaminants cancause defects. Accordingly, it is necessary to maintain a high level ofcleanliness during all or nearly all stages of production of these typesof flat media. The flat media described may be referred to below as“wafers”, although it will be understood that “wafers” means any form offlat media.

Wafers are typically processed in batches. For example, in manufacturingsemiconductor chips, for use in computers, telephones, televisions, andother electronic products, silicon wafers will undergo many batchprocessing steps, such as oxidation, photolithography, diffusion,chemical vapor deposition, metallization and etching. Batch handling mayoccur throughout the entire production process, or for one or moreprocessing steps or related handling operations. Batch processing ofthis type almost always utilizes some type of carrier or container tohold the wafers being processed.

A wafer carrier or container holds a group of wafers. The wafer carrierscan be of various designs, and may be more specifically referred to as awafer boat. In many applications, they are made of a suitable polymericmaterial, e.g., polypropylene or TEFLON® fluoropolymer. The sides andsometimes the bottom of the wafer boat have receiving slots formed toreceive and hold the wafers in a spaced array with the faces of thewafers adjacent to one another. Typically, the central axes of thewafers are aligned. The wafers are slid into the carrier or container,such as from the side or above, and are removed by sliding themoutwardly. The receiving slots are shallow so that the wafer is engagedonly at the peripheral edges and along a thin marginal band extendinginwardly from the periphery.

Wafer carriers can also be provided in the form of a protective case orbox in which the wafers are held and are sealed against contaminationduring travel within the processing facility. Wafer carriers of thistype are frequently designed to hold a wafer boat having a complementarydesign. The complementary relationship of the protective wafer carrierbox and the wafer carrier boat allow the boat and supported wafers to befully enclosed and securely held in place during transport. The term“carrier” referred to below means a carrier, a container, with orwithout a lid, or a wafer boat.

At certain stages in the manufacturing process, the wafer carriers mustbe cleaned. Cleaning them is difficult because they typically havefeatures which include slots, grooves or apertures, and inside cornerswhich can trap contaminants. The difficulty in cleaning is enhanced bythe extremely low contamination levels which are required for processingthe wafers.

Accordingly, cleaning of wafer carriers remains a difficult, timeconsuming and relatively costly procedure. Sticky-back labels,fingerprints, dust, metal particles, photoresist and organic chemicalsmay also contaminate the wafer carriers.

Various machines have been made and used for cleaning wafer carriers. Inthese machines, the carriers are mounted on a rotor and spin within achamber, while cleaning solutions are sprayed onto the carriers. Thespinning movement minimizes process time and also helps in drying thecarriers. In certain applications, surfactant is introduced and mixedwith de-ionized water, at a concentration of approximately 1:10,000.Used in this way, a surfactant acts as a wetting agent which helps toremove loosely adhered particles. Typically the surfactant is used onlyonce and then discarded as waste.

The surfactant is typically held in a vessel from which it must betransferred into the wafer carriers during the cleaning process. Sincethe surfactant stream is applied in such small flow volume so as toproduce the desired small concentration level, it is difficult tocontrol volume flow of the surfactant into the carriers. In one systemas described in U.S. patent application Ser. No. 09/113,440, surfactantis pumped from the bulk storage vessel into a holding tank where it isdiluted to a desired level. The diluted surfactant solution is thendrawn out of the holding tank by a venturi into the water stream whereit is mixed or aspirated with the water. The water and surfactantmixture is then directed to the rinsing manifold ready for injectioninto the wafer carrier.

Accordingly, it is an object of the invention to provide an improvedmachine for cleaning carriers and containers for flat media.

SUMMARY OF THE INVENTION

Apparatus for cleaning flat media carriers includes a rotor rotatablymounted within a chamber. Nozzles within the chamber are arranged tospray a washing mixture of water and a detergent or surfactant ontocarriers supported on the rotor. The washing mixture is prepared bydrawing out surfactant directly from a surfactant bulk storage vessel bymeans of a metering pump. The flow rate of the water is measured by aflow meter and in combination with the metering pump, a proper amount ofsurfactant is injected into the water line to produce a mixture with adesired surfactant concentration for removing contaminants.

In a second aspect of the invention, the surfactant solution is injectedinto the water line at or upstream of an inline mixing control valve toensure that the water and surfactant are thoroughly mixed before beinginjected into the wafer carrier.

In a third aspect of the invention, where the wafer carrier is providedwith multiple rinse manifolds for spraying the carrier, a flow meter isprovided in the water inlet line for each manifold and a separatemetering pump is provided for injecting surfactant into each water lineto ensure that a proper amount of surfactant is injected into each waterline to produce a mixture with a desired surfactant concentration.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and features will become apparent from the followingdetailed description taken in connection with the accompanying drawings.However, the drawings are provided for purpose of illustration only, andare not intended as a definition of the limits of the invention.

In the drawings, wherein the same reference numbers denote the sameelements throughout the several views:

FIG. 1 is a front, top and right side perspective view of the presentcleaning apparatus.

FIG. 2 is a back, top and left side perspective view thereof.

FIG. 3 is a front, top and right side perspective view of the apparatusshown in FIGS. 1 and 2, with the covers removed.

FIG. 4 is a back, top and left side view thereof.

FIG. 5 is a back, top and left side perspective view with variouscomponents removed for purposes of illustration.

FIG. 6 is a front, top and right side perspective view of certain majorcomponents of the apparatus shown in FIGS. 1-5.

FIG. 7 is a perspective view of the rotor removed from the chamber.

FIG. 8 is a plan view thereof.

FIG. 9 is a section perspective view illustrating air movement throughthe apparatus.

FIGS. 10, 10A, and 10B are a schematic diagram showing fluid flow andinterconnections in the present machine.

FIG. 11 is a left front side perspective view of a preferredconfiguration for the pumping and control valve system of FIG. 10.

FIG. 12 is a rear right side perspective view of the configuration ofFIG. 11.

FIG. 13 is a schematically illustrated top view showing orientations ofspray manifolds and nozzles.

DETAILED DESCRIPTION OF THE DRAWINGS

Turning now in detail to the drawings, FIGS. 1 and 2 illustrate acarrier cleaning machine 10 having a frame 12 and housing panels 14forming an enclosure. A back door 16 and front door 16A are provided onthe front and back surfaces of the machine 10. The machine 10 isgenerally installed in a clean room, of the type used in manufacturingsemiconductors. An air filter enclosure 18 is located above the frontdoor 16A, and contains a filter which filters clean room air. An exhaustduct 26 extends out of the top of the machine 10, at the back rightcorner, and is ordinarily connected to a facility or building exhaustduct.

Referring to FIGS. 3, 6 and 9, a cylindrical chamber 24 is supportedwithin the frame 12. The chamber 24 has cylindrical side walls 25 and isclosed off on the top and bottom by a top plate 36 and a bottom plate38. The top plate 36, has a central opening 37 so that air passingthrough the filter box 18 can flow into and downwardly through thechamber 24. An exhaust plenum 50 at the lower back and right side of thechamber 24 connects to the exhaust duct 26, for moving air out of thechamber 24. A drain opening 39 at a low point of the chamber 24, in theexhaust plenum 50 drains fluids out of the chamber.

Referring to FIGS. 5, 9 and 13, outer rinse manifolds 28 (R1-R4), eachhaving e.g., 12 spray nozzles, are positioned around the outsidecircumference of the chamber 24, on the chamber cylindrical side walls25. The outer rinse manifolds 28 may be located on the outside of thecylindrical side walls 25, as shown in FIGS. 4-6 and 10, or may be onthe inside surface of the cylindrical side walls 25, so long as therinse spray nozzles 30 on the outer rinse manifolds 28 are appropriatelypositioned to spray the work pieces, i.e., the wafer carriers.

Inner rinse manifolds 29 are positioned near the center of the chamber24, with each inner rinse manifold (R5-R8) having a plurality of rinsespray nozzles 30 oriented to spray outwardly onto the work pieces (i.e.,wafer carriers, containers or lids).

Similarly, outer dry manifolds 64 (D5-D8), each having a plurality ofdry spray nozzles 66, are spaced apart around the circumference of thechamber 24, on the chamber cylindrical side walls 25. Inner drymanifolds 65 (D1-D4), each also having a plurality of dry spray nozzles66 are positioned near the center of the chamber 24. A preferredorientation of the dry manifolds (D1-D8) and the rinse manifolds (R1-R8)is shown in FIG. 13.

Referring momentarily to FIG. 10, the outer dry manifolds 64 areconnected via a distribution manifold 61 and then by fluid lines 63 to asupply 120 of pressurized gas such as air or nitrogen via control valve63 a. Similarly, the inner dry manifolds 65 are connected via adistribution manifold 68 and then by fluid lines 67 to a pressurized gassupply 130 via control valve 67 a. The outer rinse manifolds 28 areconnected via a distribution manifold 141 then by fluid lines 140 to acontrol valve 170 and a source 110 of de-ionized (DI) water. The innerrinse manifolds 29 are connected via a distribution manifold 151 andthen by fluid lines 150 to a control valve 180 and the DI-water source110. Pressurized gas lines are also connected to the spray manifolds,for purging, via the control valves 170, 180. A boost pump 46 increasesthe water pressure of the DI-water from the external source 110 to therinse manifolds 28 and 29.

The control valves 170, 180 are preferably mixing control valves whichensure that the surfactant is thoroughly mixed with the DI-water.

Referring to FIGS. 3-6, and 10-12, a surfactant tank or bottle 35 isconnected to surfactant metering pumps 48 and 49 via a fluid line 190.The surfactant metering pump 48 is connected to the mixing control valve170 via fluid lines 192. Pump 48 pumps surfactant from the tank orbottle 35 into the control valve 170 where it is mixed with the DI waterfor injection into the outer rinse manifolds 28 via fluid lines 140. Thesurfactant metering pump 49 is connected to the control valve 180 viafluid lines 194. Pump 49 pumps surfactant from the tank or bottle 35into the control mixing valve 180 where it is mixed with the DI waterfor injection into the inner rinse manifolds 29 via fluid lines 150.

The drain opening 39 at the bottom of the chamber 24 leads to a diverter90 which connects the drain opening 39 to either a reclaim tank 42 or toa facility waste drain 92.

On the surfactant side, a return line 142 from fluid line 192 proximatethe mixing control valve 170 provides for priming of surfactant (underthe control of control valve 145) back to vessel 35; and a return line152 from fluid line 194 proximate the mixing control valve 180 providesfor priming of surfactant (under the control of control valve 155) backto vessel 35. On the DI-water side, a recirculation line 147 from fluidline 115 proximate the mixing control valve 170 provides forrecirculation of DI-water; and a recirculation line 157 from fluid line117 proximate the mixing control valve 180 provides for recirculation ofDI-water. The recirculation lines 147 and 157 provide a flow of waterthrough the tool even when the tool is idle to prevent bacteriaformation in lines and valves.

Referring momentarily to FIG. 9, air heaters 58 are provided within anair inlet plenum 56 behind the air filter box 18 and over the center orinlet opening 37 leading into the top of the chamber 24. Blanket heaters55 are also provided around the top of the chamber 24. Acomputer/controller 112 is linked to and controls the various pumps,valves, heaters, and flow sensors.

Referring to FIGS. 6-9, a rotor 70 is rotatably supported within thechamber 24 on a base 104. The rotor has a top ring 72 and a bottom ring74 connected by a frame work 75. Ladders 76 are pivotally supported onupper and lower ladder supports 82 extending radially outwardly from thetop ring 72 and the bottom ring 74. Each ladder 76 has a plurality ofcompartments 78 for holding containers or carriers 85, or container lids87, as shown in FIG. 9. The configuration of the ladders 76 and thedesign of the compartments 78 on the ladders 76 are adapted for thespecific sizes and types of carriers, containers, and lids to becleaned. The entire rotor 70 is rotatably supported on a center column100 and a rotor axle 106 within the center column 100. A rotor drivemotor 102 spins the rotor 70. The detailed design features of the rotor70, center column 100 and rotor axle 106 are well known, and aredescribed in U.S. Pat. No. 5,224,503, incorporated herein by reference.Alternately, the tool may be constructed with non-rotating ladders.

In use, the machine 10 is typically installed in a silicon wafer orother flat media manufacturing facility. As the wafers are moved throughvarious processing steps, the carriers 85 become contaminated, and mustbe cleaned before wafers are replaced into the carriers. The door 16 or16A of the machine 10 is opened. The rotor 70 is turned or indexed untila ladder 76 is aligned with the door. The ladder 76 is then turned 180°so that the empty compartments 78 can be accessed through the door 16.The carriers 85 are loaded into the compartments 78 and the ladder isturned back to its original position, so that the compartments 78 arefacing to the inside of the chamber 24. The ladders 76 are preferablyprovided with a latch or detent to lock the ladders into the closed oroperating position, with the compartments 78 facing the inside of thechamber 24. The next ladder 76 is then brought into alignment with thedoor, for loading, by turning the rotor 70 (by hand or via control ofthe rotor drive motor 102). Loading continues until all of the ladders76 are filled.

A facilities panel 40 on the machine 10, as shown in FIG. 6, hasconnections to input de-ionized water and gas, e.g., nitrogen or airinto the machine 10, and a connection for the waste drain 92, as well asgauges and valves for measuring and controlling fluid/gas flow.

The surfactant tank 35 is supplied with a detergent or surfactant, forexample, Valtron DP 94001 (a high pH alkaline detergent) a preferredsurfactant for removing photoresist. The term “surfactant” as used inthis application means a surfactant or a detergent. The controller 112,via appropriate control of valves and pumps, delivers DI-water andsurfactant into the mixing control valves 170, 180 to make a desiredDI-water/surfactant mixture for injection into each of the rinsemanifolds 28, 29. The DI-water boost pump 46 boosts the water pressurein the supply line 114 to deliver DI-water to both mixing control valve170 and mixing control valve 180. A flow meter 116 is disposed in thefluid line upstream of the outer rinse mixing control valve 170 tomeasure the flow of DI-water being supplied thereto. Similarly, a flowmeter 118 is disposed in the fluid line upstream of the inner rinsemixing control valve 180 to measure the flow of DI-water being suppliedthereto.

The system is initially calibrated by using information from the flowmeter 116 in combination with controls on the metering pump 48 to set areasonably precise surfactant concentration for the DI-water/surfactantmixture for injection into the outer rinse manifolds 28. Similarly, thesystem is calibrated by using information from the flow meter 118 incombination controls on the metering pump 49 to set a reasonably precisesurfactant concentration for the DI-water/surfactant mixture forinjection into the inner rinse manifolds 29. Preferably, the solution is1:10000 surfactant, with the balance being DI-water, for each of themanifolds, but having separate flow control/metering, the surfactantconcentration levels may be individually set.

The metering pumps 48, 49 are preferably a type of positive displacementpump, such as a diaphragm pump. The flow rate of such a diaphragm pumpmay be adjusted by adjusting the pump stroke (which sets the pumpingvolume per stroke) and/or the pump speed (strokes per minute). The pumpsare preferably set at a relatively high speed so that surfactant isdelivered into the system at a less pulsed/intermittent manner.

The system operator may adjust the surfactant/DI-water concentration byadjusting the pump stroke (which sets the pumping volume per stroke)and/or the pump speed (strokes per minute).

Though the system may be operated by having a preset pumping rate forthe metering pumps 48, 49 and surfactant/DI-water concentration, anelectronic control system may be implemented, using inputs from flowmeters 116, 118 and electronic control of the pumping rates of themetering pumps.

A low-level sensor 35 a may be provided on the surfactant vessel 35 foralerting that the fluid level in the vessel is low and needsreplacement. The sensor 35 a may either be a liquid sensor inside thevessel, or capacitive sensor located outside the vessel, or some othersuitable device. The sensor may just determine when the level hasreached a particular (low) level, indicating time for surfactantreplacement, or certain types of sensors may provide a signalcorresponding to surfactant level. For example, the tray 35 b (see FIG.11) in which the vessel 35 is inserted may comprise a load cellsupporting the surfactant vessel 35 to provide the weight of the vessel35 with the change in weight of the vessel as determined by the loadcell providing an indication of fluid level.

The controller 112 controls the rotor drive motor 102, causing the rotor70 to spin in a first direction, at a low speed, e.g., 1-50 rpm. Viacontrol of the pumps 46, 48, 49 and valves 170, 180, theDI-water/surfactant solution is sprayed onto the carriers 85 on thespinning rotor.

After a sufficient duration e.g., 3-10 minutes, the rotor 70 reversesdirection while the surfactant solution spraying continues, for improvedspray coverage. The inner rinse manifolds 29, located inside of therotor 70, spray radially outwardly from the center of the chamber 24.The outer rinse manifolds 28, located around the chamber cylindricalside walls 25 spray radially inwardly toward the chamber center. Thisdual spray action, combined with bi-directional rotation of the rotor70, provides virtually complete coverage of all surfaces of thecontainers 85.

After completion of application of the surfactant solution, themanifolds are purged by gas or nitrogen flowing through check valves143, 153 and the control valves 170, 180 as shown in FIG. 10.

During the surfactant wash cycle, the diverter valve 90 is positioned todirect fluid to the facility waste drain 92. Typically, as the machine10 begins the rinse cycle, the diverter 90 remains in position toconnect the drain opening 39 to the facility waste drain 92. DI-water issprayed onto the carriers 85 from all of the rinse manifolds (R1-R8),with the rotor 70 spinning in a first direction, and then reversing andspinning in the opposite direction, e.g., at from 1-50 rpm, preferablyabout 6 rpm. The heaters 58 are then turned on, and the rotoraccelerated up to e.g., 300 rpm, so that water droplets on thecontainers 85 are centrifugally flung off of the containers, and thecontainers are dried. The blanket heaters 55 are located on the outsideof the top of the chamber 24 and are on continuously, for warming thetop of the chamber. The DI rinse water goes out the waste drain 92.

If desired, for example in a water circulation mode where DI-water(without surfactant) is circulated through the chamber, the divertervalve 90 may be switched to a closed position.

While the machine 10 is useful for cleaning various contaminants, thespecific cleaning parameters, such as duration of surfactant, rinsewater, and air/gas spray, rotation speeds and sequences, heateroperation, surfactant concentration, etc., may be varied somewhat toachieve optimum results, with different containers and contaminants, aswould be apparent to one skilled in the art from the descriptionsherein.

Surfactants are generally not flammable or explosive, and do not havethe same environmental disadvantages associated with solvents. On theother hand, surfactants can be very expensive, e.g., $40/gallon. Usingthe metering pumps to produce a precise and consistent concentration ofsurfactant for the DI-water/surfactant mixture, the system conservessurfactant. The system may also use the surfactant reclaimationtechniques of U.S. Pat. No. 6,432,214 hereby incorporated by reference.

Thus, a novel cleaning machine and method has been shown and described.Various changes can, of course, be made without departing from thespirit and scope of the invention. The invention, therefore, should notbe restricted, except to the following claims and their equivalents.

1. A method for cleaning flat media carriers, comprising: spinning thecarriers about a spin axis; pumping surfactant out of a storage vessel;mixing the surfactant with a predetermined amount of water to obtain amixture of surfactant and water; and spraying the mixture of surfactantand water onto the carriers.
 2. The method of claim 1 with the pumpingperformed via a flow metering pump, further including setting a flowrate of the flow metering pump to achieve a desired concentration ofsurfactant in the mixture of surfactant and water.
 3. The method ofclaim 1 with the mixing performed via a mixing control valve.
 4. Themethod of claim 3 further including measuring the amount of waterflowing into the mixing control valve.
 5. The method of claim 3 furtherincluding adjusting the amount of surfactant pumped out of the storagevessel based on the measured amount of water flowing into the mixingcontrol valve.
 6. The method of claim 1 further including stopping therotor and then spinning the rotor in a reverse direction.
 7. The methodof claim 1 further including spraying the mixture of surfactant andwater in a radial inwardly direction from a first outer spray manifold,and also spraying the mixture of surfactant and water in a radialoutwardly direction, from a second inner spray manifold.
 8. A method forremoving contaminants from flat media carriers, comprising: loading thecarriers onto a rotor within a flat media carrier cleaning machine;spinning the rotor; spraying a water/surfactant mixture onto thecarriers via an inlet line by: injecting water into the inlet line;measuring the flow of water entering the inlet line; pumping surfactantfrom a storage vessel into the inlet line using a flow metering pump;mixing the surfactant and water to obtain a surfactant/water mixture;and setting flow rate of the flow metering pump to achieve a desiredconcentration of surfactant for the surfactant/water mixture.
 9. Themethod of claim 8 further comprising discontinuing pumping surfactant;and rinsing the carriers by spraying the carriers only with water. 10.The method of claim 9 further comprising discontinuing injecting ofwater into the inlet line; and drying the carriers by spraying thecarriers with a dry gas.
 11. The method of claim 10 wherein the dry gascomprises nitrogen or air.
 12. The method of claim 8 wherein the watercomprises de-ionized water.
 13. The method of claim 8 further comprisingspinning the rotor at from 1-50 rpm while spraying the mixture towardthe carriers.
 14. The method of claim 8 further comprising adjustingflow rate of surfactant being pumped into the inlet line by adjustingoperation of the metering pump.
 15. The method of claim 8 wherein thesurfactant and water are injected into the inlet line via a mixingcontrol valve.
 16. A method for cleaning one or more containers,comprising: spinning the rotor; supplying DI water to the mixer at aknown flow rate; pumping surfactant from a storage vessel to a mixer viaa flow metering pump; adjusting the amount of surfactant pumped out ofthe storage vessel based on the flow rate of water flowing into themixer; mixing the surfactant with water at the mixer, to obtain amixture of surfactant and water; and spraying the mixture of surfactantand water onto the containers.